Dielectric thin films are used in many devices, such as display devices or capacitors. Particularly in electroluminescent display devices, the dielectric thin film may be one of yttrium oxide. An economic technique for preparing the thin film is by high rate sputtering using vacuum equipment including a vacuum chamber. The source material for sputtering is in the form of a sputtering target, comprising one or more solid pieces from which material is evolved by ion bombardment. The target is usually mounted on a backing plate. High power loading needed for high sputtering rates results in a need for substantial heat dissipation through the rear side of the target to the backing plate. The backing plate is usually made of copper or some other good heat conductor.
A number of problems have been encountered in the forming of a stable, intimate bond between the target and its backing plate. For instance, mechanical bond failure has occurred wherein the target separates from the backing plate. Targets are often mounted vertically to minimize contamination and there is a tendency for them to separate from the backing plate if the bond is weak. Another problem encountered is the cracking of the target due to inadequate heat transfer between the target and its backing plate. This problem is exacerbated in the case of magnetron sputtering, used for high rates, wherein the surface of the target is not heated uniformly. Another problem that has been encountered is the evolution of contaminants from the bonding material. For example, epoxies evolve organics that ruin the thin film. A bonding material of solder might be considered, but it has been found that solder materials do not stick effectively to a dielectric layer such as one of yttrium oxide, nor to a wide class of other materials such as ceramics.